A cooling system includes a unit for processing product to be cooled or frozen. A secondary refrigeration loop is connected to this unit and introduces a refrigerant at or near atmospheric pressure into the unit. The secondary refrigeration loop may be open or closed. The secondary loop includes a secondary heat exchanger for cooling the refrigerant. A primary, closed refrigeration loop, operating at a pressure of not less than 2 atmospheres, includes a forward flow path which comprises a primary refrigerant compressor for producing compressed primary refrigerant, a primary heat exchanger for receiving and cooling the compressed primary refrigerant and an expander for further cooling and transferring the compressed refrigerant to the secondary heat exchanger to enable cooling of the secondary refrigerant. The primary loop further includes a return flow path from the secondary heat exchanger to the primary refrigerant compressor and to the primary heat exchanger. The primary heat exchanger thereby provides heat exchange from the return flow path to the forward flow path to accomplish a cooling action.